/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.obfuscate;

import proguard.classfile.*;
import proguard.classfile.attribute.Attribute;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.util.SimplifiedVisitor;

/**
 * This AttributeVisitor marks all attributes that it visits.
 *
 * @see AttributeShrinker
 *
 * @author Eric Lafortune
 */
public class AttributeUsageMarker extends SimplifiedVisitor implements AttributeVisitor {
    // A visitor info flag to indicate the attribute is being used.
    private static final Object USED = new Object();

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {
        markAsUsed(attribute);
    }

    // Small utility methods.

    /**
     * Marks the given VisitorAccepter as being used (or useful). In this context, the VisitorAccepter will be an
     * Attribute object.
     */
    private static void markAsUsed(VisitorAccepter visitorAccepter) {
        visitorAccepter.setVisitorInfo(USED);
    }

    /**
     * Returns whether the given VisitorAccepter has been marked as being used. In this context, the VisitorAccepter
     * will be an Attribute object.
     */
    static boolean isUsed(VisitorAccepter visitorAccepter) {
        return visitorAccepter.getVisitorInfo() == USED;
    }
}
